"""

"""

def uf_find(n,p):

    ufl = []

    while p[n] != n:
        ufl.append(n)
        n = p[n]

    for i in ufl:
        p[i] = n

    return n


def uf_union(a,b,p,rank):

    ap = uf_find(a,p)
    bp = uf_find(b,p)

    if ap == bp:
        return True
    else:

        if rank[ap] > rank[bp]:
            p[bp] = ap
        elif rank[ap] < rank[bp]:
            p[ap] = bp
        else:
            p[bp] = ap
            rank[ap] += 1

        return False

import sys
from sys import stdin

N,M = map(int,stdin.readline().split())

ctop = [None] * (N+1)

p = [i for i in range(M+1)]
rank = [0] * (M+1)
ans = 0

for i in range(N):

    b,c = map(int,stdin.readline().split())

    if ctop[c] == None:
        ctop[c] = b
    elif not uf_union(ctop[c],b,p,rank):
        ans += 1

print (ans)